Traces of humanity: What aliens could learn from the stuff we’ve left in space

From The Boston Globe:

Moon If you were to visit the moon today, in the neighborhood of the Apennine mountain range, you would find a small figurine, about the same size and shape as a Lego minifigure, lying facedown in the lunar dust. Unauthorized by NASA, this “Fallen Astronaut” sculpture was placed there exactly 40 years ago this past week by astronauts David Scott and James Irwin of Apollo 15, and sits alongside a tiny plaque listing the names of 14 astronauts and cosmonauts who had died during their time in their respective space programs. This haunting miniature memorial is only one of the many artifacts and messages that human beings have deliberately sent into space, or left there, as a symbol of our presence. On Earth, most of human history has involved unconsciously leaving traces of our existence, from garbage to aqueduct ruins. But when we go into space, we can begin to make choices about what we leave to posterity.

Even in space, where none of us live, some of what we’ve left is space junk: stuff orbiting the earth that nobody particularly intended to leave anywhere. But much of what we’ve left in space is intentional. Some of it is symbolic artifacts intended for an audience of people here on Earth – the fallen astronaut, the American flag on the moon, a CD containing a list of over half a million people who wanted to send their names to a comet, courtesy of a NASA probe. In some cases, however, we are also sending a deliberate signal out beyond Earth, to be received by forces unknown. Rather than just listening for radio signals, which has been a staple of the Search for Extraterrestrial Intelligence, some earthlings have become interested in actively reaching out – broadcasting radio messages to anyone, or anything, out there that might be able to hear them.

More here.